The present invention relates to a cooling method and to the associated apparatus.
Various cooling methods and associated cooling arrangements have already been proposed and are in widespread use in various branches of the industry and elsewhere. Among such uses, there is simple cooling, refrigeration, freezing and the use in cryogenics. There has been already proposed a method in which a cooling medium is circulated in at least one cooling circuit in which the cooling medium is sequentially compressed and cooled by an ambient cooling fluid, the compressed cooling medium condensed, expanded, heated, evaporated and the recirculated to a compressor. It has also been already proposed to provide at least one cooling circuit as an incorporated cascade circuit in which a mixture is used as the cooling medium and in which the condensation of the compressed cooling medium is a fractional condensation which includes at least one partial condensation. Then, the partially condensed cooling medium is subjected to a phase separation and then the cooling medium which is in the form of a condensate is supercooled by an expanded and warming up cooling medium in a countercurrent supercooling heat exchange, then expanded and then warmed up with accompanying evaporation in a countercurrent evaporative heat exchange. On the other hand, the cooling medium separated in its vapor phase is cooled in a countercurrent evaporative heat exchange and thus at least partially condensed. It has also been proposed, in this context, to thermally segregate the countercurrent supercooling and evaporation heat exchange from one another.
In the known methods, the heating of the expanded cooling medium in the countercurrent evaporative heat exchange, and the heating of the expanded cooling medium in the countercurrent supercooling heat exchange are performed in series after one another, that is, the expanded cooling medium enters, after its issuance from the countercurrent evaporative heat exchange, the countercurrent supercooling heat exchange at the cold end thereof. Thus, the cooling medium is subjected to a considerable temperature rise after its expansion and prior to its entry into the countercurrent supercooling heat exchange as a result of the heating and evaporation thereof in the countercurrent evaporative heat exchange. Subsequent to the expansion, the cooling medium will usually be substantially in its liquid phase at or close to its boiling point, which contributes to the thermodynamic optimization of the method in that the temperature of the cooling medium remains virtually unchanged during the expansion. In order that the cooling medium which enters the countercurrent supercooling heat exchange at the cold end thereof be capable of cooling the cooling medium to be supercooled down to this temperature, the temperature rise experienced by the cooling medium in the countercurrent evaporative heat exchange must be compensated for by the admixture of a substantial amount of the cooling medium which is at a considerably lower temperature than the cooling medium to which it is admixed. A mixture of cooling media which are at substantially different temperature, however, detracts from the thermodynamic optimization of the method.